I only need to say this once. I rebuilt my os .12 cv with a duratrax ABC piston and sleeve and I'll never do it again. I broke the engine in properly and was very nice to it for 10 tanks. I didn't finish getting the quart through it and it had lost a good deal of compression. It's next to impossible to start now. When I do another rebuild, I'm going with the O.S. parts, the originals lasted for 3-4 gallons.